Fault characteristics and their petroleum geology significance:A case study of well Shun-1 on the northern slope of the central Tarim Basin

The geometric characteristics, active stages and formation mechanism of strike-slip faults in well Shun-1 area on the northern slope of the central Tarim Basin were studied through 3D seismic interpretation and combined with fault throw and fault growth index analyses. The study area has clear layered characteristics. Deep structures are mainly of linear strike-slip faults; middle structures are primarily normal faults which group sinistralen echelon and form horst-graben structures, locally forming negative flower structures with a basement strike-slip fault. Small-scale normal faults are developed in shallow structures. Basement strike-slip faults have formed in the middle Caledonian and activated again associated with en echelon normal faults in Silurian during the early Hercynian. The thick Sangtamu Formation mudstone of the Upper Ordovician is identified as a detachment layer, which resulted the decollement between the basement strike-slip fault and its cover. This region has experienced magmatism and widespread extension in the late Hercynian. The rejuvenation of basement strike-slip faults resulted in the local strong compression in the latest Hercynian and fault-related folds in the Indosinian.In the latest Hercynian, basement strike-slip faulting was linked with en echelon normal faults, which could be favorable hydrocarbon migration paths. Strike-slip induced folds cut by en echelon normal faults, forming faulted anticlines, faulted nose and fault blocks, could be favorable traps for petroleum accumulation. The Ordovician palaeokarst that developed extensively near strike-slip fault zones, is an important future target for petroleum exploration.